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<! "@(#)prepare.so 10.8 (Sleepycat) 9/29/98">
<!Copyright 1997, 1998 by Sleepycat Software, Inc. All rights reserved.>
<html>
<body bgcolor=white>
<head>
<title>Berkeley DB: DbTxn::prepare</title>
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btr
ee,hash,hashing,transaction,transactions,locking,logging,access method,access me
thods,java,C,C++">
</head>
<h1>DbTxn::prepare</h1>
<hr size=1 noshade>
<tt>
<h3>
<pre>
#include <db_cxx.h>
<p>
int
DbTxn::prepare();
</pre>
</h3>
<h1>Description</h1>
<p>
The DbTxn::prepare method initiates the beginning of a two-phase commit.
<p>
In a distributed transaction environment, Berkeley DB can be used as a local
transaction manager. In this case, the distributed transaction manager
must send <i>prepare</i> messages to each local manager. The local
manager must then issue a DbTxn::prepare and await its successful
return before responding to the distributed transaction manager. Only
after the distributed transaction manager receives successful responses
from all of its <i>prepare</i> messages should it issue any
<i>commit</i> messages.
<p>
The DbTxn::prepare
method either returns <b>errno</b> or throws an exception that
encapsulates an <b>errno</b> on failure, and 0 on success.
<p>
<h1>Errors</h1>
If a fatal error occurs in Berkeley DB, the DbTxn::prepare method may fail and either
return DB_RUNRECOVERY or throw an exception encapsulating DB_RUNRECOVERY,
at which point all subsequent database calls will also fail in the same
way. Methods marked as returning <b>errno</b> will, by default, throw
an exception that encapsulates the error information. The default error
behavior can be changed, see <a href="../../api_cxx/DbException/class.html">DbException</a>.
<p>
The DbTxn::prepare
method may fail and throw an exception
for any of the errors specified for the following Berkeley DB and C library
functions:
abort(3),
fcntl(3),
fflush(3),
fprintf(3),
free(3),
getpid(3),
<a href="../../api_cxx/DbLog/put.html">DbLog::put</a>,
malloc(3),
memcpy(3),
memset(3),
strerror(3),
vfprintf(3),
and
vsnprintf(3).
<p>
<h1>Class</h1>
<a href="../../api_cxx/DbTxn/class.html">DbTxn</a>
<p>
<h1>See Also</h1>
<a href="../../api_cxx/DbTxn/abort.html">DbTxn::abort</a>,
<a href="../../api_cxx/DbTxn/commit.html">DbTxn::commit</a>,
<a href="../../api_cxx/DbTxn/id.html">DbTxn::id</a>
and
DbTxn::prepare.
</tt>
</body>
</html>
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